(1) Technical Field
This invention relates to methods for preventing particulate contamination on semiconductor substrates during photoresist baking and more particularly, to an apparatus for preventing condensed photoresist vapor from flaking off an exhaust plate during barrier and reflective coating bake (BARC).
(2) Description of the Prior Art
The following four documents relate to apparatus dealing with the processing of semiconductor substrates for forming integrated circuits. A thin film of material, for example, a photoresist that is suspended in a solvent, is applied to the surface of a semiconductor substrate. To harden the material, the thin film must be baked and then cooled.
U.S. Pat. No. 6,291,800B1 issued Sep. 18, 2001 to Shirakawa et al. discloses a hot plate and exhaust port design.
U.S. Pat. No. 6,229,116B1 issued May 8, 2001 to Shirakawa et al. shows a hot plate apparatus.
U.S. Pat. No. 6,228,171B1 May 8, 2001 to Shirakawa. and U.S. Pat. No. 6,185,370B1 relates to hot plate designs.
The use of a thin layer of photo resist on a wafer's surface in conjunction with photolithograhic masks provides the means to transfer various masking layers onto the substrate. The photolithographic mask selectively exposes a portion of photoresist film to actinic light while leaving the masked portion unexposed. The exposed portion makes the photoresist soluble in a base solution and insensitive to light. The unexposed portion is insoluble in the base solution and is photosensitive. The development of highly integrated circuit patterns with line widths and spacing in the sub micron ranges places increasingly higher demands on image resolution capabilities of the photoresist. Processes involving film thickness, thickness uniformity, resist baking, and intermediate handling have become critical steps in the manufacturing of high speed integrated circuits.
The focus of this invention is directed to a photoresist-baking chamber, and more particularly, to a modification of a plate cover such as that used over a deep temperature hot plate, manufactured by Tokyo Electric Ltd., Japan. This invention is concerned with the elimination of a source of contamination originating during baking of the photoresist. The baking procedure, namely pre-bake and post bake is done in conjunction with resist coating, exposing, and resist develop cycles. The heat energy is conventionally supplied with hot plates having a built-in resistance heater. During the baking process, the coated substrate rests on a plurality of short stand-off projections which creates a short space between the hot plate and substrate, thereby heating the substrate and baking the photoresist by the transference of heat by radiation, convection and conduction. The air and solvent vapor surrounding the hot plate is heated and rises up to a conically shaped plate and exhausted through an exhaust port located at its center. The centered port collects and evacuates most of the vapor, however, a dead zone of stagnated vapor condenses on the under side of the cover that eventually dries, flakes off, and falls causing particulate contamination to adhere to the substrate.